The reported structure of the "putative prismane" protein from Desulfovibrio vulgaris
indicates that it contains a hybrid [4Fe-2S-3O] cluster ligated by seven protein residues,
three cysteines, one persulfido-cysteine, two glutamates and one histidine. The sequences
of at least six other closely homologous proteins have been found, five of these from complete
genomes. In three sequences, the hybrid cluster is associated with an amino terminal [4Fe-4S]
cluster, while in the sequence from Escherichia coli it is associated with a [2Fe-2S]
cluster. In the sequence from Methanobacterium thermoautotrophicum, it may be associated
with a rubredoxin-type center. The nickel-containing chain of carbon-monoxide dehydrogenase
also has a domain with some sequence similarities to the hybrid cluster proteins. The
nickel-containing cluster in carbon-monoxide dehydrogenase may be structurally related to the
hybrid [4Fe-2S-3O] cluster. Models have been prepared for the hybrid [4Fe-2S-3O] and the nickel
hybrid clusters in the RESID Database, distributed by the Protein Information Resource (PIR)
and made available on the Website at